1. Field of the Invention
The present invention relates to a-printing press with a sheet-turning-over-mechanism for turning over a printing sheet, enabling the printing press to be selectively operable in a one-sided printing mode and a double-sided printing mode, and, in particular relates to a printing press with a sheet-turning-over-mechanism that is capable of properly dealing with a failure occurred during a mode switching operation for switching from the one-sided printing mode to the double-sided printing mode or vice versa.
2. Description of the Background Art
Conventionally, along with diversified printing needs, printing presses with the sheet-turning-over-mechanism selectively operable in the one-sided printing mode and the double-sided printing mode have been known.
In such a printing press with the sheet-turning-over-mechanism, where a failure has been detected by a detection switch or a sensor during the operator carries out the mode switching operation for example from the one-sided printing mode to the double-sided printing mode, a safety switch is activated upon the detected information to stop the entire operation of the printing press to stop the mode switching operation. Thus, it is possible to secure the safety of human bodies during the operator carries out the mode switching operation and prevent machine damages.
The printing press can be forcibly or manually stopped by, for example, pressing a stop button by the operator during the mode switching operation, thereby enabling securing the safety of human bodies and preventing machine damages.
Thus, in order to secure the safety of human bodies or to prevent machine damages, the entire operation of the printing press and hence the mode switching operation are stopped by the manual operation by the operator (pressing the stop button) or by the automatic activation of the safety switch. The detection of any failure by the detection switch or sensor represents the presence of a failure in the sheet-turning-over-mechanism. Accordingly, the mode switching operation needs to be stopped since the continuous mode switching operation might cause a damage or breakdown of the printing press.
In order to suspend the mode switching operation, it is necessary to stop the entire operation of the printing press, which may result in troubles not only in a sheet transferring operation, but also the entire operation of the printing press after restarting the printing press. Moreover, when the entire printing press is to be suspended for some reasons in the course of fine adjustment in some step, such fine adjustment is inevitably suspended. As a result, an adjustment error may be caused in an operation after restarting the printing press, so that it is difficult to resume the operation with precise adjustment. Therefore, in the case when the operation is finished with poor adjustment, such poor adjustment might cause a failure in sheet transferring operation.
Moreover, as described above, where, during the mode switching operation, the entire operation of the printing press has been stopped by manually pressing the stop button by the operator, the automatic activation of the safety switch upon detecting a failure by the detection switch or sensor, or a power failure, the operator needs to recover the printing press to a normal operable state by fixing such a failure by using tools.
However, in a printing press with such a full automatic sheet-turning-over-mechanism, the aforesaid fixing and recovering operation requires special skills which may not be possessed by an operator. If an erroneous fixing and recovering operation is carried out by the operator with no such special skills, damages might be caused in the printing press. For this reason, the operator usually does not carry out a manual recovering operation and, instead, calls a service person with such special skills. As a result, the printing press cannot be operated until the service person has arrived at a customer having the printing press, and fixed the failure and recovered the printing press to a normal operable state. Consequently, once such an unusual situation occurs, the printing press must be stopped with the mode switching operation suspended, leading to significantly lowered productivity of printing operation.
In order to solve these problems, for example, Japanese Patent Publication No. 2878801 discloses a safety device for a sheet-fed printing press with a sheet-turning-over-mechanism, which is designed to retain the information representative of a state of the mode switching operation at the moment of the stop of the printing press. According to this prior-art technique, a keep relay provided in this printing press retains, based upon the function of a stepping relay, the information as to which state of the mode switching operation proceeded. At the same time, a main motor of the printing press is electrically interlocked so as to be held in a stop state during the mode switching operation, based upon contact points of the keep relay. Accordingly, even when the power-supply is turned off for any reason during the mode switching operation, a step at the moment of this turning-off is retained in the keep relay, enabling the printing press to be restarted from an uncompleted step or reproduce a state immediately before the turning-off of the power-supply by again turning on the power supply. As a result, the printing press is less likely to fail in a proper start from the step to be resumed. Also, it is possible to ensure safety in the mode switching operation since the main motor is held in the interlocked state even when the power-supply has been again turned on.
However, in the prior art technique of this type, the keep relay retains the information as to the ongoing mode switching operation on a step basis, with the result that, for example, when the mode switching operation is suspended between steps, it is not possible to precisely retain a state at the moment of the suspension of the mode switching operation. As a result, it is difficult to resume the mode switching operation from the suspended state, even if the operator has restored the printing press to a normal operable state.
Also, where the sensor or switch for detecting a failure of the mode switching operation did not operate properly and hence the printing press has been stopped during the mode switching operation, there is a possibility that the mode switching operation cannot be resumed even after the recovering operation. In this case, it is necessary to perform an operation for having the printing press operable in a one-sided printing mode or double-sided printing mode. Since this operation is manually done, the workload for the operator is increased.
In either case, there is a problem to take a time and involves a troublesome work for recovering the printing press to a normal operable state from a state with the mode switching operation suspended.
The present invention has been conceived in order to solve the aforesaid problems. It is an object of the present invention to provide a printing press with a sheet-turning-over-mechanism that is capable of easily recovering from its state with the mode switching operation suspended and properly or precisely resuming the mode switching operation based upon the detailed or accurate information.
According to one aspect of the present invention, there is provided a printing press with a sheet-turning-over-mechanism for turning over a printing sheet, enabling the printing press to be selectively operable in a one-sided printing mode and a double-sided printing mode. The printing press includes a controller which, when any failure stops any one of steps of a mode switching operation for switching the printing press from the one-sided printing mode to the double-sided printing mode or vice versa, stores the information representative of a state of the mode switching operation at the moment of the stop due to the failure, and when a normal operable state is restored from the failure, resumes the mode switching operation from a step of the mode switching operation indicated by the operational state stored therein.
With the printing press having the above arrangement, when a failure has stopped any step of the mode switching operation, the controller, which stores the information representative of a state of the mode switching operation at the moment of the stop due to the failure can resume the mode switching operation from a step of the mode switching operation indicated by the operational state stored therein, when a normal operable state is restored from the failure. That is, since a state of the ongoing mode switching operation is continuously or non-stepwisely stored in the controller, an abrupt or unexpected stop of the mode switching operation due to a power failure, an emergency operation of the stop switch by the operator or an activation of the safety switch can be properly dealt, thereby enabling the operational state of the mode switching operation to be precisely stored. Specifically, the mode switching operation can be resumed precisely from its state or step at the moment of the stop of the mode switching operation. As a result, there may cause no trouble with the printing press in resuming the mode switching operation from the step which has been suspended.
The controller preferably includes failure detecting means for detecting a failure in the sheet-turning-over-mechanism during the mode switching operation; operation stopping means for stopping the mode switching operation at the time of the detection of the failure by the failure detecting means; memory means for storing the information representative of a state of the mode switching operation at the time when the mode switching operation has been stopped by the operation stopping means; and operation resuming means which, when the sheet-turning-over-mechanism is restored to a normal operable state, resumes the mode switching operation from a step of the mode switching operation indicated by the operational state read out from the memory means.
According to the above arrangement, when a failure has been detected by the failure detecting means during a mode switching operation, the mode switching operation is stopped by the operation stopping means, while the memory means stores the information representative of a state of the mode switching operation at this time. When a normal operable state is restored from the failure, the operation resuming means reads out the information from the memory means and resumes the operation from a step of the mode switching operation indicated by the operational state. Accordingly, the mode switching operation can be resumed precisely from its state or step at the moment of the stop of the operation, with the result that there may cause no trouble with the printing press in resuming the mode switching operation from the step which has been suspended.
The information representative of the operational state of the mode switching operation preferably includes step numbers respectively allocated to the steps of the mode switching operation.
According to the printing press with the step number included in the information representative of the operational state, the mode switching operation can be resumed from a step corresponding to the step number, which has been suspended due to the stop of the mode switching operation with an improved precision.
According to another aspect of the present invention, there is provided a printing press with a sheet-turning-over-mechanism for turning over a printing sheet, enabling the printing press to be selectively operable in a one-sided printing mode and a double-sided printing mode. The printing press includes a controller which, when any failure stops any one of steps of a mode switching operation for switching the printing press from the one-sided printing mode to the double-sided printing mode or vice versa, stores the information representative of a state of the mode switching operation at the moment of the stop due to the failure, returns the sheet-turning-over-mechanism to a state before the start of a step of the mode switching operation indicated by the operational state stored therein, and resumes the mode switching operation from said step.
With the printing press having the above arrangement, when a failure has stopped any step of the mode switching operation, the controller, which stores the information representative of a state of the mode switching operation at the moment of the stop due to the failure can return the sheet-turning-over-mechanism to a state before the start of a step of the mode switching operation indicated by the operational state stored therein and resume the mode switching operation from said step. Thus, it is not necessary for the operator or service person to manually return the sheet-turning-over-mechanism to a state to be resumed.
According to still another aspect of the present invention, there is provided a printing press with a sheet-turning-over-mechanism for turning over a printing sheet, enabling the printing press to be selectively operable in a one-sided printing mode and a double-sided printing mode. The printing press includes a controller which stores the information representative of a state of the printing press before a mode switching operation for switching the printing press from the one-sided printing mode to the double-sided printing mode or vice versa is started, and when a failure stops any one of steps of the mode switching operation, returns the printing press to the state before the mode switching operation is started.
With the printing press having the above arrangement, the controller stores the information representative of a state of the printing press before the controller starts the mode switching operation, and returns the printing press to the state before the mode switching operation is started. Accordingly, where the mode switching operation cannot proceed, the printing press is returned to a state enabling a first side printing operation if it is the operation completed just before the stop of the mode switching operation. Likewise, the printing press is returned to an operable state enabling a second side printing operation if it is the operation completed just before the stop of the mode switching operation. As a result, the printing press can perform either the first side printing operation or the second side printing operation. Here, the first side printing operation means the operation in which a first side of each sheet is printed in the upstream side of the sheet-turning-over-mechanism, while the second side printing operation means the operation in which a second side of each sheet is printed in the downstream side of the sheet-turning-over-mechanism.